Scanning mechanism



Nw. 243.-, i959 H. BLACKSTGNE.

SCANNING MEcHANsM Y Filed March 26, 1959 2 Sheets-Sham l IN1/EN TOR.

MEA/AW @Mc/Www Arm/Magni Nov. Z4, 3959 H. BLACKSTONE ZSQM@ SCNNING MECHNISM Filed March 26, 1959 2 Sheets-Sheet 2 INVENTOR f my@ ATTORNEYS' agitata Faizenteci Nov. 24,

free l pas SCANNNG MECHANHSE Henry Blackstone, Syosset, NEI., assigner to Servo Corporation of America, New Hyde Park, NX., a corporation of New York Application March 26, 1959, Serial No. 302,145

9 Claims. (Ci. 17g-6.8)

My invention relates to an improved optical-scanning means and to radiation-responsive means utilizing such optical scanning.- The present application is a continuation-inpart of my copending application, Serial No. 339,- 701, filed March 2, 1953.

It is an object of the invention to provide improved optical-scanning means of the character indicated.

it is another object to provide improved means for continuously and automatically scanning a field of View for varying energy levels in such field.

It is a further object to provide improved display means for scanning means of the character indicated.

It is a specific object to meet the above objects with a mechanism which may make a single-shot exposure over a field of view and which will operate automatically and with simple controls for the full duration of such exposure.

Another specic object is to provide simplified recycling means for a single-shot exposing device of the character indicated.

A further specific object is to provide means for more eiciently scanning a `eld of view, the dead or nonutilized scanning time being reduced to substantially zero.

Other objects and various further features of novelty and invention will be pointed out or will occur to those skilled in the art from a reading of the following specifi'- cation, in conjunction with the accompanying drawings. In said drawings, which show, for illustrative purposes only, preferred forms of the invention: t

Fig. l is a simplied view in perspective illustrating major elements of a scanning device incorporating features of the invention;

Fig. 2 is an enlarged View partly broken away and in perspective, and partly electrically schematic, to illustrate coordinated functioning in the device of Fig. 1;

Fig. 3 is an electrical circuit diagram illustrating a control circuit employed in conjunction with elements of Fig. 2; A

Fig. 4 is a View similar to Fig. 2, but illustrating a modilication; and

Fig. 5 is a diagram schematically illustrating an alternative of the form of Fig. 4.

Briefly stated, my invention contemplates what might` be termed a camera analog of a scanning system of the general character set forth in the above-identified co- -pending patent application. The basic scanning means may comprise energy-responsive means iixedly carried by a support; collecting optics focused on the energy-responsive means inay be journalled for rotation on the support. The support itself is mounted for what may be termed scan-depression movement with respect to a frame, and means coordinated with the scan-depression movement may determine limits of operation of signal-processing means for the output of the energy-responsive means, thereby determining limits of a single-shot exposure over a scanned iicld of view.

Throughout the specification reference will be made to about a vertical axis.

`the movement of the support with respect to the frame as a scan-depression movement, but it will be understood that these words do not necessarily limit the desired or preferred movement of the support. For example, in certain cases it may be desirable that the scan-depres sion movement involve for each exposure an upward progression about a horizontal axis. Alternatively, a right-tO-left or left-toright movement may be involved In any case, the motion will be understood to be about an axis generally transverse to the scanning `axis and to be adequately described by the term scan-depression.

Referring to the drawings, my invention is shown in application to a device incorporating two units which may, for convenience, be mounted at two spaced locations and interconnected by flexible means 10. Thus, a scanner unit 11 may be mounted on a tripod 12 with its viewing aperture 13 facing the subject matter or eld to be scanned; signal-processing means for the energy detected in the scanner of unit 11 may be largely contained in a separate cabinet unit 14- including, if desired, a panel 15 at which a recording chart may display a permanent record of scanned information, and a cathoderay display device 16 for more transient examination of the exposure. y

The scanning means may comprise energy-responsive or detector means 17, such as a photocell, bolometer, or the like, depending upon the energy spectrum of interest, and fixedly carried as by a standard 18 mounted on support means 19. The support means 19 in turn may be movably mounted with respect to the frame or cabinet 11, and I have suggested in the drawing that the support 19 may be pivotly mounted on shaft means 20w-0', journalled as at Z1 in side walls of the cabinet 11. The scanning means may include one or more objective elements such as lenses, carried for rotation about an axis transverse to the axis of shaft means Ztl-20', but I have shown such objectives to include a plurality of spaced mirrors 22-23-24, focused at a common point on detector means 17, which happens to be shown mounted on the scanning axis and in the plane defined by the optical axes of the mirrors. The mirrors 22- 3- .Z4 may be equally spaced about the scanning axis to define a generally cylindrical drum, and this spacing preferably equals the width of the mirrors.

The ring Z5 will be understood schematically to designate bearing means for supporting one end of the scanning drum, as against a bearing or guide member 25 on support means 19; at the other end of the scanner, similar support means 26 may include a toothed periphery to permit motor drive, `as by means 27 mounted on a bracket 28 forming part of the support means 19.

Signal-processing means responsive to the output of the energy-responsive means 17 may include a pre-ampliier 3) mounted directly at the base of standard 13 and on the support means 19. Signals may thus be elevated to a level permitting ready transmission by line 10 to suitable further amplifying means 31-32 in the cabinet 14. For display on the cathoderay tube 16, the output of ampliiier 31 may provide direct intensitymodulation, and a horizontal-sweep generator 33 may be synchronized with rotation of the drive motor 27 to gen erate the horizontal-sweep signals, the sweep rate being the number of mirrors (3) times the speed of the scanner drum.

1f a moving-film camera is to record a succession of horiozntal sweeps on the tube 16, then no vertical sweep is necessary, because the total picture development will be the result of cordinated movement of the camera iilm with succeeding sweeps. However, in the form shown, I illustrate the employment of a vertical sweep as generated by means 34 coordinated with the rotation of 3 the scan-depression shaft 26. Thus, if the persistance of the viewing screen at tube i6 is of sufficient duration, there may be a fully developed field image on tube i6, as when making a trial exposure.

lt is inherent in the described scanner that one half the scanning time cannot be utilized by any single sensitive element at 17. This results rom the need to bring each optical system 22`23-24i successively into and out of the scanning iield, and the time thereby necessarily taken. During this waste period, which occurs between each succeeding optical sweep, signals from detector IC7 will be spurious, and resort should be made to shutter means (as at detector i7, but not shown), or to synchronized blanking means (as disclosed in the said copending application), or to other means to avoid presentations of the spurious signals. In the form shown, I employ a mask 16 set over the face of tube 11.6 and of a size to mask video traces from all but the desired signals, thus presenting only the desired rectangular field.

Ordinarily, I prefer that permanent records be made of the field scanned by the means thus far described, and for this purpose l illustrate a stylus-operated moving-strip recorder including` take-up and supply reels 35--36 for electrically sensitive recording paper, iilm, or the like 5.52, to be advanced over a platen 37. On the other side of the paper 42, a stylus 38 may be driven transversely of the paper advance and in synchronism with the scanning movement of the optics. The stylus 3S is shown to be carried at one point along a flexible conductive loop stretched over spaced pulleys 399-40, and if desired, other styli 38-33 may also be carried by the stylus loop, at equally spaced locations. Signals from amplifier 32 are fed to the stylus 3@ through brush or slip-ring means 41 and via the drive shaft for.

pulley 39. Recordings, are made upon discharge through the sensitive paper, or the like 42 to the platen 37, which is shown grounded. Spurious signals may be eliminated during successive waste periods by suitably proportioning the spacing between styli to the desired edective width of the recording paper 42., as by limiting the transverse conductive length of platen 37 (suggested by dotted outlines).

The parts thus far described will operate to produce a perfectly satisfactory record or picture of the energy collected through a scanned eld of View as seen through the window i3 which is preferably of a size to permit inclusion of limiting rays for all extremes of the scanned lield, and which is also, of course, of a material transparent to the radiation of interest. However, for added convenience, l prefer that exposure be made as upon a simple manual initiating operation and that thereafter all functions be governed automatically. Thus, motor means 45 may, through reduction gearing i6 47, drive the scan-depression shaft 2f) between iixed limits, as determined by limit-switch means 4349- An arm 50 carried on the shaft may contact one or the other of the limit-switch means 43--49 to determine limits of scan depression. In certain cases, it may be desirable to maintain a given relationship between the scan speed and the scan-depression rate, and I suggest at 45 that a synchronizing connection between drives 27-45 may produce this result.

Referring to Fig. 3, it will be seen that the limit-switch means 45S may be of the double-pole variety, as suggested by the two circuits shown in Fig. 3 under the control of switch means 4S; for the form shown, each pole is of the normally closed variety. Limit-switch means 49 may also be normally closed. Manual selector-switch means may include a rst arm Slt connected in one circuit to determine the energizing of a winding 52 for forward (eg. exposure) drive of the motor 45, and a second arm S3 ganged to the arm 5l may determine the energizing of a reverse Winding for motor 52. Thus, depending upon the setting of the switch means Slt-53 aaifaeoa which may involve a single manual operation as suggested in the drawing, the circuits may be conditioned for forward or reverse operation, corresponding to exposure and recycling of the described equipment. I ordinarily prefer that the switch means 5?.-53 be of the springoperatcd type, requiring manual hold-in forthe reverse condition, so that once the parts have been recycled, spring-operated means (not shown, but inherent in switch means Sl-Sle) may recondition the circuits for exposure.

ln order to initiate an exposure and, of course, once the scanning means is brought up to a steady continuous rotation of desired speed, a single manual switch 55 need only be depressed to complete the forward-drive circuit for motor d5. At the time switch 55 is closed, the parts may be in the relaion shown in Fig. 2, with the arm dil actuating the switch means 558 and, therefore, providing an opening in both circuits to motor 45. However, once the forward or exposure drive has been started, switch means i8 will no longer be actuated, so

that it may return to its normally closed condition to hold-in the forward-drive circuit for motor 155.

ln order that the signal-processing -means may be caused to supply the display only during an exposure, l have shown relay means including a winding 5'6 in series with the forward-drive circuit, so that the nor mally open contact arm 57 thereof will only closel a vcircuit when an exposure is being made. The circuit Aclosed upon operation of relay 56 will be understood to .provide a control function to the signal-processing means, and at 52 in Fig. 2 I suggest thatthis may be merely a video ori-oli bias control, as in amplier Si. Thus, unless the motor means 42,5 is driven in a forward direction, and only when it is so driven, will there be any exposure and, therefore, display or recording.

At the end of scan depression for the exposure or forward drive, arm Si) will actuate switch means 49 to open the circuit to forward winding S2 of motor 45, thus terminating both the display and the scan-depression drive. If the forward-reverse switch means 51--53 should accidentally be left in the position shown, no further actuation of switch 55 will harm the equipment, because switch i9 will hold the forward-drive circuit open. However, upon shifting selector switch 51S3 to the reverse position, the circuit for reverse winding 54 will be closed and the circuit for forward Winding 52 held open, while recycling takes place; recycling is complete when the parts reach the relation shown in Fig. 2, that is, when arm S0 strikes switch i3 and both forward and reverse circuits are thereby automatically opened.

As noted above, the basic scanning mechanism described in Fig. 2 has the inherent limitation that only 50 percent of the actual scanning time is utilizable to derive information for display. For most purposes, this limitation may not be consequential. However', as when it is necessary to make a faster exposure for coverage Aof the iield of view, it may be desired to approach a 10D-percent time-utilization of the scanning mechanism. Therefore, in Fig. 4 l illustrate a mechanism which may accomplish greater scanning eiliciency.

ln the arrangement of Fig. 4, l actually employ two scanning optical systems, each of which happens to have -an odd number of concave mirrors as the focusing elements. These systems are driven in synchronism, and 4they are shown mounted on the same rotating assembly, with the mirrors 69 of one system in angularly staggered relation with those 6l of the other system. Each system is shown to include its own separate non-rotated energyresponsive means 62-63 with individual pre-amplifier means oaf- 65, Shield means 5ST may be non-rotatably supported on the same means (not shown) as that for the energy-responsive means 6263 and may include a sulicient angular opening to deline limits for the desired iield of view. Gating means 65 operating in synchronism with the drive 67 for the rotating assembly provides a.

horizontal-sweep circuit 70 may be synchronized with i gate operation and with rotation of the scanning assembly. Permanent records may be available in accordance with the recording methods illustrated in Fig. 2, but in Fig. 4 I show optical means 71 for projecting the dis" play images of tube 69 onto a moving recorder film or paper 72.

As in the case of Fig. 2, the scanning mechanism of Fig. 4 may be suspended by support means (not shown) for inclination about a scan-depression axis 75, as driven by motor means 76 and gear means 77, corresponding to that described at 45-46-47 in Fig. 2. For bettercoordinated automatic operation, advance of the recorder lm or paper 72 may be synchronized with scan-depression movement, as suggested by the line 78; also, for greater uniformity of development of any given exposure, synchronizing means 79 may establish a fixed relation between the speeds of the two motors 67-76- If desired, automatic control of the display elements of the signalprocessing means may he effected in Fig. 4 by means completely analogous to that described in Fig. 2, so as to assure automatic sequencing of operations for a singleshot exposure.

In operation, for either of the described scanning coniigurations, it is not necessary to provide a geared or otherwise directly synchronized relationship between rotary drive of the scanning drum and drive to the scandepression mechanism. This will apply if each of the energy-responsive means 17-62-63 comprises but a single sensitive element so as to constitute the basis for a single scanning spot -in the iield of view. If, as may in certain cases be desirable, the energy-responsive means 17, or 62-63, should comprise a plurality of separate elements, electronically commutated as disclosed in the said copending patent application, then, of course, each one of these elements for a particular energy-responsive means will constitute a diiierent scanning spot across the eld of view; for a perfect presentation or display, the lines resulting from this multiplicity of scanning spots should be evenly spaced. To assure this, the suggested synchronism at 4:? 79 must exist between the scanning drive (as at 27 or 67) and the scan-depression drive (as at 45 or 76),

When employing the arrangement of Fig. 4 to scan objects at infinity, or effectively so, the energy-responsive means 62-63 need only be placed at the center of scan rotation and in the planes of the optical axes of their respective optical systems. Thus for such conditions, the axial spacing between the elements 62-63 is preferably coincident with the spacing between optical axes of the mirrors S0- 61. This, of course, implies that for no scan depression and for objects at, or substantially at, inlinity, the two scanning systems 643-61 will alternate in their coverage of the same line in the field of View. If it is desired that the two scanning systems shall alternate for scanning lines of given spacing, then the sensitive elements 62-63 may be eccentrically displaced with respect to the non-axis arrangement specified as preferred.-

`For coverage of fields at close range, of course, parallax will constitute a problem if the sensitive elements 62-63 are on the optical axes of mirrors 6661, respectively, and if these optical axes are parallel. For special cases in which it is known what the focusing distance will be, it would certainly be possible to build the scanning drums Sil- 61 with a pre-set convergence of optical axes. However, for flexibility in use, I provide what may be termed rough-focusing means apparl allax-correction means in the form of a differential axial adjustment in the relative positioning of the sensitive elements 62-63. Such adjustment may be made by rst rack-and-pinion means 8i) operative to displace the element 62; and, if desired, second rack-and-pinion means 81 may displace the sensitive element 63. A single manual adjustment knob 82 may control the desired relative displacement, and for small parallax corrections the resulting eccentric employment of the mirrors will be found not to introduce too substantial a degrading of optical quality.

Itwill be 'appreciated that the arrangement of Fig. 4 provides a means whereby the video output of the sensitive element 62 is interlaced with that of the element 63. In other words, when the device is focused in a given field, each of the sensitive elements 62-63 scans essentially the same line across the field, the only difference being one of time. In aircraft-reconnaissance applicationsl wherein the rotary axis is generally aligned with the iiight axis of the aircraft, and wherein the window opening is downward beneath the aircraft, the line-scanning action is transverse of the flight path, and the time spacing between line scans of course means a progression of separate scan lines on the ground, so that the sensitive elements (S2-63 provide a means whereby twice the number of lines can be developed by the apparatus in a given period of time. The same scan-interlace relation applies for a fixed (eg. tripod-mounted) camera wherein a scan-depression motion is employed, as disclosed in Fig. 2.

Fig. 5 shows a modification of Fig. 4 wherein the same scan lines can be interlaced by two gated cells to provide essentially the same type of increased coverage of the eld of view. In the arrangement of Fig. 5, however, the optics include a scanning or continuously rotating mirror polygon 90, which is shown as a hexagonal prism continuously driven by the motor means 67. The two energy-responsive elements 62-63 are served by this same scanning polygon and are shown placed at fixed but angularly separated locations, so as to successively scan the line 91 in the field of view, in interlaced relationship. For the instant depicted in Fig. 5, and for direction of rotation indicated by arrow on the polygon 90, the image 63 is developing its first response in the line 91 as it begins to be swept from left to right. At the same instant, the image 62 of the cell 62 has just completed its full scan of the line 91, so that at the next instant the polygon 9i) will have advanced incrementally,

,and there will be no need for further observation of the output of the cell 62. The amplifiers 64-65 and gating means ld5 are as previously described for Fig. 4, and it will be appreciated that the action is such as to connect to the display means 16 only'the video output of that particular cell 62 or' 63 which happens instantaneously to be scanning the line 9i. The result is that there is no dead time when any particular cell has completed its line scan, because immediately thereafter the next cell has begun its line scan, resulting in complete line interlace.

Iclaim:

l. `Optical-scanning means, comprising two like pluralities of focusing means, each plurality comprising like focusing means equally angularly spaced about a common axis of rotation and having"separate optical axes convergent toward said common axis, relatively fixed energy-responsive means substantially in the focal surface of focusing means of each said plurality, whereby upon rotation of said pluralities successive focusing means of each plurality will be brought into focus on said energy-responsive means, the focusing means of one plurality being angularly staggered with respect to the focusing means of the other plurality.

2. Scanning means according to claim l, in which said energy-responsive means includes a separate responantenas .f a] sive element for each said plurality of focusing means, and gating means synchronized with rotation of said focusing means and connected to said separate elements, whereby the output `of said gating means may reflect f successive samplings of the Outputs of said elements.

3'. Optical-scanning means, comprising two like pluralities of focusing means, each plurality comprising like focusing means equally angularly spaced about a common axis of rotation and having separate optical axes convergent toward said common axis, separate relatively iixed energy-responsive means substantially in the focal Surface `of focusing means of each said plurality, whereby upon rotation of said pluralities successive focusing means of each plurality will be brought into focus on said i energy-responsive means, the focusing means of one plurality being angularly staggered With respect to the Jfocusing means of the other plurality, and adjust-ably positioni Iable means supporting one of said energy-responsive means for movement relatively to the other of said energy-responsive means.

4. Scanning means according to claim 3, and including further adjustably positionable means supporting the other of said energy-responsive means.

5. Scanning means according to claim 4, and means differentially interconnecting said adjustably positionable means.

infrared-responsive means and then by the other infraredresponsive means, signal-processing means including gating means connected to the outputs of both said infraredresponsive means, and a synchronizing connection between said gating means and said continuously rotated mirror means.

7. A device according to claim 6, in which said mirror means comprises a separate focusing mirror for each of said infrared-responsive means, both said focusing mirrors being xedly related to each other and therefore .rotated in unison.

8. device of claim 6, in which said mirror means is a mirror polygon, and in which said optics further include separate focusing elements individually serving each of said infrared-responsive means, said polygon mirror serving both said focusing systems.

ln a device of the character indicated, two relatively fixed infrared-responsive means, scanning optics including continuously rotated mirror means imaging both said infrared-responsive means between first and second limits along a line in a eld to be scanned as said mirror means is rotated, the respective positions of each of said infraredresponsive means with respect to said mirror means being such as to alternate the scanning of said lines first by one infrared-responsive means and then by the other infraredresponsive means, display means including gating means connected to the output of both said infrared-responsive means, a synchronizing connection between said gating means and said continuously rotated mirror means, said display means including sweep means synchronized with successive lines scanned by said respective infrared-responsive means in succession, whereby said display means No references cited. 

